This is a perfect example of a problem asking for the LCM (Least Common Factor). If every 6th person in line gets a prize, and every 8th person gets a prize, then those are the two numbers you have to use to find the LCM. Now let's list the multiples of both numbers:
6: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60
8: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80
What is the first number you see that both numbers (6,8) have? I see 24 as the first number. So, in the line, the first person to get both the theater ticket and the gift card of $30 will be the 24th one. Hope this helps! :D
When rounding to three decimal places, you consider if the number to the right of the third decimal place is less than or greater than 5. If it's less than 5, then the digit in the third decimal place stays the same. If it is greater than or equal to 5, then you round the digit in the third decimal place up by one.